• ~user2/something.wad should fetch from /home/user2/something.wad, not /home/user1/user2/something.wad or /home/user1user2/something.wad.


• ~/foo/~bar/something.wad should fetch from "/home/user1/foo/~bar/something.wad" (second tilde is escaped), not /home/bar/something.wad.


• On Windows, for compatibility reasons a path beginning with ~ may optionally map to %HOMEDIR% (e.g. C:\Documents and Settings\user1 or C:\Users\user1 in example). Or, %HOMEDIR% could be supported too on Windows (if not already so).

/**
 * @brief Resolution mechanism for paths that can contain dynamically
 * resolvable placeholders.
 *
 * Allowed placeholders are:
 *
 * * `$PROGDIR` (capitals important) resolves to the directory where
 * the application's executable resides.
 * * `$` character followed by a letter or underscore followed optionally
 * by a string of letters, digits or underscores is treated as an env.
 * variable and resolution using such variable is attempted. If there's
 * no matching env. variable, the placeholder resolves to an empty string.
 * Regex: `$[a-zA-Z_][a-zA-Z0-9_]*`.
 * * `~` character at the beginning, followed by a directory delimiter
 * or end of the string is replaced with user's home directory.
 * The `~user` pattern is not allowed and will be treated as
 * a "~user" literal.
 *
 * While Windows platform quotes the env. variables with `%`, DataPaths
 * doesn't follow this pattern and uses the `$` prefix universally for
 * all platforms.
 *
 * @return Path with all placeholders resolved as best as possible.
 * The returned path is not normalized.
 */
QString resolveTemplated(const QString &templatedPath) const;

Quote from "WubTheCaptain"
QFileInfo in Qt 5 definitely supports tilde.